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Wireless Communications, IEEE Transactions on

Issue 9 • Date September 2006

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Displaying Results 1 - 25 of 41
  • IEEE Transactions on Wireless Communications - Table of contents

    Page(s): 1
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  • Transactions letters - Layered group detection for multiuser mimo wireless cdma systems

    Page(s): 2305 - 2311
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    In this paper, we consider a multiuser multiple input multiple output (MIMO) CDMA system where each user is transmitting different streams spread with the same code on a set of multiple antennas. Signals from one user are received as one group and each user is thought of as a virtual group. At the receiver, group ordered successive interference cancellation detection is applied. Optimal and sub-optimal group detection orders that maximizes the system performance are then derived. Various linear group detectors are considered such as the linear decorrelators and a closed form expression of the optimal order is given for the case of each of these group detectors. Numerical results demonstrate significant gains in the system performance as well as the importance of group ordering View full abstract»

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  • Discrete stochastic programming by infinitesimal perturbation analysis: the case of resource allocation in satellite networks with fading

    Page(s): 2312 - 2316
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB) |  | HTML iconHTML  

    This paper deals with a NP-hard resource allocation problem for a satellite network. An approach based on the estimation of the gradient of a cost function, obtained through a "relaxed continuous extension" of the discrete constraint set, is proposed. Since neither closed forms of the performance measure, nor additional feedbacks on the statistical properties of the traffic sources are requested, the proposed approach reveals to be suitable for optimizing the resource allocation in real life case studies, where the application of specific certainty equivalent assumptions is impractical View full abstract»

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  • Practical approaches to channel estimation and interference suppression for OFDM-based UWB communications

    Page(s): 2317 - 2320
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (341 KB) |  | HTML iconHTML  

    Ultra-wideband (UWB) communication is a potential technique for future high-speed networks. In this paper, we investigate channel estimation and interference suppression for OFDM based UWB systems. In particular, we modify an existing channel estimation approach for UWB systems and develop an exponential window based approach to estimate correlation of the receive signals for interference suppression. Computer simulation results show that these approaches can be effectively used in OFDM based UWB systems View full abstract»

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  • Opportunistic multipath for bandwidth-efficient cooperative multiple access

    Page(s): 2321 - 2327
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB) |  | HTML iconHTML  

    Within a new paradigm, where wireless user cooperation is viewed as a form of (opportunistic) multipath, we exploit the unique capabilities of direct-sequence spread spectrum transmissions in handling multipath to design a novel spectrally efficient protocol for wireless cooperative networks. We show how and why our proposed system achieves diversity without increasing bandwidth. After analyzing its performance, we deduce that user capacity can be significantly improved with respect to existing third generation cellular systems in the uplink View full abstract»

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  • MGF-based performance analysis of selection diversity with switching constraints in nakagami fading

    Page(s): 2328 - 2333
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB) |  | HTML iconHTML  

    This paper focuses on the performance evaluation of selection combining (SC) diversity with switching constraints over independent non-identically distributed (i.n.i.d.) Nakagami-m fading channels. New closed-form expressions for the moment generating function (MGF) of the SC output signal-to-noise ratio (SNR) in Nakagami-m fading channels, as a function of channel decorrelation, have been obtained. These expressions have been the starting point to derive performance measures like average combined SNR, outage probability, and average bit error probability of various modulation schemes View full abstract»

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  • Beam-pattern-scanning dynamic-time block coding: achieving high performance

    Page(s): 2334 - 2337
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB) |  | HTML iconHTML  

    In this paper, we introduce a novel transmit diversity in which the space diversity in space-time block codes (STBC) is combined with time diversity created by beam pattern scanning (BPS). Via this merger, we achieve high bit-error-rate (BER) performance via time diversity inherent in BPS and space-time codes in STBC. A dynamic time (that is, time-varying) block coding (DTBC) is introduced to compensate the effect of time varying array vectors applied to the array elements in BPS. Hence, we call the scheme BPS dynamic time block coding (BPS/DTBC). We discuss the structure of the BS antenna array and receiver, and generate the BER performance simulations View full abstract»

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  • Rate maximization in multi-antenna broadcast channels with linear preprocessing

    Page(s): 2338 - 2342
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    The sum rate capacity of the multi-antenna broadcast channel has recently been computed. However, the search for efficient practical schemes that achieve it is still ongoing. In this paper, we focus on schemes with linear preprocessing of the transmitted data. We propose two criteria for the preceding matrix design: one maximizing the sum rate and the other maximizing the minimum rate among all users. The latter problem is shown to be quasiconvex and is solved exactly via a bisection method. In addition to preceding, we employ a signal scaling scheme that minimizes the average bit-error-rate (BER). The signal scaling scheme is posed as a convex optimization problem, and thus can be solved exactly via efficient interior-point methods. In terms of the achievable sum rate, the proposed technique significantly outperforms traditional channel inversion methods, while having comparable (in fact, often superior) BER performance View full abstract»

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  • Optimum training symbol design for MIMO OFDM in correlated fading channels

    Page(s): 2343 - 2347
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (315 KB) |  | HTML iconHTML  

    Multiple transmit and receive antennas (MIMO) have been used with orthogonal frequency division multiplexing (OFDM) for capacity improvement in frequency-selective channels. In certain propagation environments, there exists spatial correlation among channels corresponding to different pairs of transmit and receive antennas. In this paper, we investigate training sequence design for channel estimation in MIMO-OFDM systems. We develop necessary conditions for a training sequence to minimize the mean-square error (MSE) of channel estimation when spatial correlation of MIMO channel is known to the transmitter and discuss training sequence design for some special cases. The performance improvement of the designed training sequences is confirmed by simulation examples View full abstract»

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  • An improvement for authentication protocol in third-generation wireless networks

    Page(s): 2348 - 2352
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (457 KB) |  | HTML iconHTML  

    An improvement for the mutual authentication in the third-generation mobile networks is proposed to address the potentially long delay in waiting for authentication vector (AV) when SGSN and HLR/AuC are located far away from each other, or when the two entities are operated by different operators, or when the mobile terminal (MT) call/mobility activity is frequent. In the 3GPP Technical Specification TS33.102, the probability that an action triggering authentication and key agreement (AKA) has to wait for an AV is fixed as high as 20%. Our proposed scheme is able to achieve this probability smaller than 2% with negligible increased signaling overhead and low storage cost View full abstract»

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  • Receive antenna selection in MIMO systems using convex optimization

    Page(s): 2353 - 2357
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (326 KB) |  | HTML iconHTML  

    A critical factor in the deployment of multiple-input multiple-output (MIMO) systems is the cost of multiple analog transmit/receive chains. This problem can be mitigated by antenna subset selection at the transmitter/receiver. With antenna selection, a small number of analog chains are multiplexed between a much larger number of transmit/receive antenna elements. In this paper, we present a low complexity approach to receive antenna selection for capacity maximization, based on the theory of convex optimization. We show via extensive Monte-Carlo simulations that the proposed algorithm provides performance very close to that of optimal selection based on exhaustive search. We also, extend this approach to receive antenna selection for the JMMSE and OSIC V-BLAST architectures View full abstract»

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  • Performance modeling of MIMO OFDM systems via channel analysis

    Page(s): 2358 - 2362
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (321 KB) |  | HTML iconHTML  

    Multiple-input multiple-output (MIMO) antennas can be combined with orthogonal frequency division multiplexing (OFDM) to achieve diversity gain and/or to increase system spectral efficiency through spatial multiplexing. In this letter, we derive the probability density function (pdf) expressions of the condition number (i.e., the maximum-to-minimum-singular-value ratio, MMSVR) of the channel state information (CSI) matrix. We show that this ratio is directly related to the noise enhancement in open-loop MIMO systems and provides a significant insight on the overall system capacity. The pdf of this ratio could be used to predict the relative performances of various MIMO configurations without complex system-level simulations. The pdf can also be used to compute the probability of whether certain channels fail in the high-throughput mode. Extensive simulations are performed to validate the accuracy of the closed-form pdf of the MMSVR derived in this letter View full abstract»

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  • Large penalty of hybrid diversity with uncoded modulation in slow rayleigh fading

    Page(s): 2363 - 2368
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (399 KB) |  | HTML iconHTML  

    In hybrid selection/maximal ratio combining (H-S/MRC) the receiver selects the L branches with the largest signal-to-noise ratios (SNRs) from N available diversity branches and performs maximal ratio combining (MRC). A penalty is incurred with respect to MRC which can be defined as the increase in SNR required for H-S/MRC to achieve the same symbol error probability as MRC. Recently, this penalty was investigated specifically for two-dimensional modulations. In this paper, we derive the asymptotic SNR penalties in slow Rayleigh fading for small and large values of SNR for general uncoded signaling constellations View full abstract»

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  • Transactions Papers - Space-time-frequency characterization of MIMO wireless channels

    Page(s): 2369 - 2375
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (719 KB) |  | HTML iconHTML  

    In this paper, we characterize the cross-correlation function (CCF) between the time-frequency transfer functions (TF)s of two sub-channels of a multiple-input multiple-output (MIMO) wireless fading channel. The TF of each sub-channel consists of a number of multi-path components caused by propagation of a transmitted signal in random scattering media. The proposed CCF is expressed in terms of several environmental parameters (such as the moment generating function (MGF) of the delay profile (DP) and the pathloss exponent). It is a summation of two terms: the first term is due to the autocorrelation of multi-path components while the second term is due to the cross-correlation of multi-path components. Each term is a product of several correlation functions. Each of these correlation functions represents different dependencies of the wireless channel in terms of time, carrier frequency and the position of the antenna elements around both the transmitter and the receiver site. Interestingly, the last two terms of these functions are (n/2)-order (or n-order) integrations of the MGF of the DP, evaluated at two carrier frequencies (or the difference between carrier frequencies), where n is the pathloss exponent of the environment View full abstract»

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  • MASK: anonymous on-demand routing in mobile ad hoc networks

    Page(s): 2376 - 2385
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB) |  | HTML iconHTML  

    The shared wireless medium of mobile ad hoc networks facilitates passive, adversarial eavesdropping on data communications whereby adversaries can launch various devastating attacks on the target network. To thwart passive eavesdropping and the resulting attacks, we propose a novel anonymous on-demand routing protocol, termed MASK, which can accomplish both MAC-layer and network-layer communications without disclosing real IDs of the participating nodes under a rather strong adversary model. MASK offers the anonymity of senders, receivers, and sender-receiver relationships in addition to node unlocatability and untrackability and end-to-end flow untraceability. It is also resistant to a wide range of attacks. Moreover, MASK preserves the high routing efficiency as compared to previous proposals. Detailed simulation studies have shown that MASK is highly effective and efficient View full abstract»

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  • A spectral domain approach to design spreading sequences for DS-CDMA systems in frequency selective fading channels

    Page(s): 2386 - 2395
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (653 KB) |  | HTML iconHTML  

    In this paper, we propose a frequency domain approach to design a set of spreading sequences for a DS-CDMA system in the presence of frequency selective fading. We show that the number of parameters involved in the design of optimal spreading sequences can be made smaller when they are analyzed in the frequency domain, than when they are analyzed in the time domain. Further, it is shown that for multipath channels, designing a set of spreading sequences in the frequency domain reduces to assigning a spreading sequence for each user with a spectrum whose spectral lines are located at the strongest spectral components of the user's channel's spectrum while keeping the cross correlation at a very low value for spreading sequences with overlapping spectra. We show that by designing spreading sequences in the frequency domain, the performance of some existing algorithms for the design of spreading sequences can be improved and/or the computational complexities can be reduced. We further show that the proposed idea can be extended to the design of spreading sequences where the chips of the spreading sequences are derived from a constant amplitude alphabet View full abstract»

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  • Performance analysis of turbo-coded APSK modulations over nonlinear satellite channels

    Page(s): 2396 - 2407
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (970 KB) |  | HTML iconHTML  

    This paper investigates the performance of M-ary amplitude-phase shift keying (APSK) digital modulation over typical nonlinear satellite channels. The effect of the satellite nonlinearity is studied, and distortion pre- and post-compensation techniques for coded APSK are presented. Moreover, clock timing, signal amplitude and carrier phase recovery schemes are discussed. For the latter, a new class of non turbo decoder-aided closed-loop phase synchronizers featuring good performance and low complexity is studied. Finally, an end-to-end coded APSK system simulator inclusive of the satellite channel model and synchronization sub-systems is discussed and its performance compared to standard trellis-coded QAM concatenated with Reed-Solomon codes, showing a remarkable gain in both power and spectral efficiency. Coded APSK, recently selected for the new standard -DVB-S2- for digital video broadcasting and interactive broadband satellite services, is shown to represent a powerand spectral-efficient solution for satellite nonlinear channels View full abstract»

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  • Capacity and error probability analysis of orthogonal space-time block codes over correlated nakagami fading channels

    Page(s): 2408 - 2412
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (326 KB) |  | HTML iconHTML  

    In this letter, system capacity and error probability of orthogonal space-time block coding (STBC) is considered for PAM/PSK/QAM modulation in correlated Nakagami fading channels. The approach is based on an equivalent scalar AWGN (additive white Gaussian noise) channel with a channel gain proportional to the Frobenius norm of the matrix channel for the STBC. Closed form capacity and error probability expressions are derived for Nakagami fading channels. Numerical results are given to illustrate the theory View full abstract»

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  • Link quality-aware call admission strategy for mobile cellular networks with link adaptation

    Page(s): 2413 - 2425
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (804 KB) |  | HTML iconHTML  

    In this paper, the performance of mobile cellular systems with link adaptation (LA) is analytically evaluated. Half- and full-rate vocoders are considered in the analysis. Mathematical expressions for the new call blocking, handoff failure, and forced termination probabilities are obtained. To our knowledge, no similar analysis considering LA exists in the literature. Also, the link quality-aware dual fractional channel reservation (LQA DFCR) scheme is proposed. In LQA DFCR, user differentiation is implemented in terms of link quality. Preference is given to users with good link quality because they require fewer resources than users with bad link quality. Numerical results show that the proposed LQA DFCR scheme effectively increases system capacity: LQA DFCR achieves more than a 11% capacity gain relative to systems with the non priority scheme (NPS) and with LA, and approximately 3% relative to the fair access prioritisation scheme (FAPS) strategy. Numerical results also show that LA yields an approximately 18% capacity increase relative to a cellular system without LA when no admission control is employed (admission control strategies further increase system capacity.) The synergy between LA and admission control strategies yields more than a 31% capacity gain View full abstract»

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  • Design and analysis of coded multiplexing for the multiuser OFDM downlink

    Page(s): 2426 - 2434
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB) |  | HTML iconHTML  

    The allocation of available resources/subcarriers is an important design aspect for next generation wireless OFDM multiuser systems. The approaches considered usually assign a subset of subcarriers to each user and do not consider the loss of coding and diversity gains when a user is allotted very few subcarriers. We investigate an approach which exploits the multiplexing diversity available in the system in the absence of channel state information at the transmitter. This is achieved by spreading the data of all users over the complete set of subcarriers by using an appropriate combination of coding, multiplexing and interleaving. The performance of such a system is analyzed and the potential for substantial coding, interleaving and diversity gains is demonstrated. This paper also outlines a new approach to evaluate performance bounds for concatenated codes with higher order modulation on a fading multipath channel, by simplifying the description of pairwise error events using an ideal modulator assumption. Simulations are presented for a suboptimal decoding scheme, which does not rely on information from other users View full abstract»

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  • Adaptive downlink multi-user MIMO wireless systems for correlated channels with imperfect CSI

    Page(s): 2435 - 2446
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1563 KB) |  | HTML iconHTML  

    Multiple-input multiple-output (MIMO) wireless antenna systems provide increases in capacity without the need for additional spectrum or power. However the capacity increase is limited when the number of antennas at the receiver is fixed or restricted (due to mobile size constraints for example). To overcome this limitation multi-user MIMO can be used, which allows several users to be served simultaneously in frequency and time. A disadvantage of these multi-user MIMO systems, when used in the downlink however, is that they need accurate channel state information (CSI) at the transmitter and also uncorrelated channels among users. In this paper we investigate methods to address the problems of multi-user MIMO systems in spatially correlated channels. We adopt the concept of angle between subspaces to characterize the inter-user spatial correlation and adapt the algorithm to those conditions. We also investigate the impact of the accuracy of CSI at the transmitter (CSIT) and whether more limited CSI such as channel correlation information alone can be used to provide good multi-user MIMO performance. Results are presented as various simulated capacity measures and we use them to make comparisons between the various multi-user MIMO configurations View full abstract»

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  • Reverse link capacity analysis of cellular CDMA systems with controlled power disparities and successive interference cancellation

    Page(s): 2447 - 2457
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1249 KB) |  | HTML iconHTML  

    This paper presents a new approach in analyzing the reverse link capacity performance of cellular CDMA systems employing successive interference cancellation (SIC). Due to the controlled power disparity present in such systems previous methods cannot precisely model their inter-cell interference. We first introduce a novel model which allows the accurate analysis and evaluation of the inter-cell interference of cellular CDMA systems with controlled power disparity. Its validity is verified by means of theoretical analysis and computer simulations. Secondly, by using this new inter-cell interference model, a theoretical analysis of the CDMA reverse link capacity is presented. In terms of evaluation results, we focus on the performance improvements SIC offers as compared to single user detection (SUD). Analytical results complemented by equivalent computer simulated performance evaluation results have shown that SIC significantly increases the reverse link capacity of cellular CDMA systems operating in realistic controlled power disparity environments View full abstract»

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  • Improved bayesian MIMO channel tracking for wireless communications: incorporating a dynamical model

    Page(s): 2458 - 2466
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (353 KB) |  | HTML iconHTML  

    This paper investigates the improved decoder performance offered by incorporating dynamic linear modelling techniques when applied to particle filters for use in tracking the MIMO wireless channel. Conventional Bayesian-based receivers that perform channel tracking necessarily require a wireless channel model, typified by the use of a low order auto-regressive (AR) model. Normally, the model parameters are static in nature and are estimated a priori of any transmission; thus if the channel conditions change, a model mismatch occurs and system performance is degraded. Our method allows for time-varying channel statistics by modelling the channel fading rate as a Markov random walk. This new procedure allows the channel model to assume a time-varying behavior. As shown through simulations, the incorporation of dynamic modelling of time-dispersive channels not only offers superior performance, but at high SNR eliminates the error-rate floor commonly seen in systems using the static AR models View full abstract»

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  • Power distribution/allocation in multirate wideband CDMA systems

    Page(s): 2467 - 2476
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB) |  | HTML iconHTML  

    A unified approach for power distribution and allocation in a multirate wideband CDMA system is investigated. It is shown that the traffic demand and the background disturbance fully govern the feasibility of the system and the optimal power distribution solutions, where the traffic demand is specified by the user QoS requirement, data rate, and spread spectrum bandwidth; the background disturbance includes the background noise and the intercell interference. Closed form expressions of the optimal power allocation, subject to power constraints in the practical system design, are derived. Convergent conditions are applied to evaluate the capacity region of the system. Numerical examples are provided to illustrate the applications of the obtained theoretical results. View full abstract»

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  • Scan and wait combining (SWC): a switch and examine strategy with a performance-delay tradeoff

    Page(s): 2477 - 2483
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (669 KB) |  | HTML iconHTML  

    This paper proposes and analyzes an alternative form of switch and examine combining, namely one that waits for a channel coherence time if all the available diversity paths fail to meet a predetermined minimum quality requirement. This scanning through the available diversity paths followed by waiting process is repeated indefinitely until a path with an acceptable quality is found. The performance of the resulting "scan and wait" combining (SWC) scheme is studied in terms of its average probability of error and ergodic capacity. The paper looks also into (i) the delay associated with SWC by deriving the statistics of the waiting time needed before satisfactory transmission occurs and (ii) the underlying complexity by studying the statistics of the number of diversity paths estimated per channel access. Selected numerical examples show that, for a fixed average number of channel estimates per channel access, SWC outperforms traditional diversity combining schemes at the expense of a negligible time delay View full abstract»

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Aims & Scope

The IEEE Transactions on Wireless Communications publishes high-quality manuscripts on advances in the state-of-the-art of wireless communications.

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Meet Our Editors

Editor-in-Chief
Jeff Andrews
Cullen Trust for Higher Education Endowed Professor of Engineering